Large moulds composed of composite material, in particular fibre-reinforced resin matrix composite material, especially those used for producing wind turbine blades, are well known in the art.
The vast majority of such moulds are produced from epoxy-fiberglass laminate, or polyester-fiberglass laminate, both of which are excellent electrical conductors. Under conditions of low atmospheric humidity however, such moulds, especially large ones such as those used for making wind turbine blades, can build up strong static electric charges. These static electrical charges mainly develop whenever the finished parts are demoulded and removed from the mould. Such static electricity can cause several problems:    1. Static charges can damage electronic equipment, such as mould heating control systems.    2. Static discharge can ignite explosive vapors.    3. Static discharge is unpleasant for workers who may touch the mould.
An additional shortcoming of the traditional composite moulding tools is the use of gelcoat as a surface layer. This gelcoat surface layer is easily cracked or debonded, since it consists of only resin with small particulate filler, and does not have any reinforcing fiber content.
This gelcoat layer has traditionally been required because epoxy-fiberglass or polyester-fiberglass mould laminate cannot obtain a satisfactory surface finish after repairing and sanding. Due to the difference in hardness between the resin and the glass, the glass fibers always emerge above the resin after sanding, resulting in a rough and unsatisfactory surface finish. Only by making the surface totally from gelcoat resin can a repairable mould be obtained.